Tofogliflozin, A Highly Selective Inhibitor of SGLT2 Blocks Proinflammatory and Proapoptotic Effects of Glucose Overload on Proximal Tubular Cells Partly by Suppressing Oxidative Stress Generation.

Ninety percent of glucose filtered by the glomerulus is reabsorbed by a sodium-glucose cotransporter 2 (SGLT2), which is mainly expressed on S1 and S2 segment of renal proximal tubules. Since SGLT-2-mediated glucose reabsorption is increased under diabetic conditions, selective inhibition of SGLT2 is a potential therapeutic target for the treatment of diabetes. We have recently shown that an inhibitor of SGLT2 has anti-inflammatory and antifibrotic effects on experimental diabetic nephropathy partly by suppressing advanced glycation end products formation and oxidative stress generation in the kidney. However, the direct effects of SGLT2 inhibitor on tubular cell damage remain unclear. In this study, we investigated the effects of tofogliflozin, a highly selective inhibitor of SGLT2 on oxidative stress generation, inflammatory and proapoptotic reactions in cultured human proximal tubular cells exposed to high glucose. Tofogliflozin dose-dependently suppressed glucose entry into tubular cells. High glucose exposure (30mM) for 4 and 24h significantly increased oxidative stress generation in tubular cells, which were suppressed by the treatment of tofogliflozin or an antioxidant N-acetylcysteine (NAC). Monocyte chemoattractant protein-1 (MCP-1) gene expression and apoptotic cell death were induced by 4h- and 8 day-exposure to high glucose, respectively, both of which were also blocked by tofogliflozin or NAC. The present study suggests that SGLT2-mediated glucose entry into tubular cells could stimulate oxidative stress and evoke inflammatory and proapoptotic reactions in this cell type. Blockade of glucose reabsorption in tubular cells by SGLT2 inhibitor might exert beneficial effects on tubulointerstitial damage in diabetic nephropathy.